Forming

Cold Forming

A bend in Plaskolite acrylic sheet can be accomplished without applying heat. A minimum radius of 200 times the thickness of the acrylic is required to avoid stress cracking.

Line Bending

Line bending is a method of forming a sharp bend in the acrylic sheet. The radius of the bend can be controlled by adjusting the width of the heated area. Routing a V-groove into the acrylic prior to bending will produce a very sharp bend. Heating elements such as nicrome wire, infrared, rods, or wide strips can be used. Heat the area to be bent to a pliable state then place the sheet in a fixture to cool (See Fig. 18 & 19).

Adjust heating time, element temperature, and distance from the heating element, dependent on acrylic thickness, to eliminate scorching and bubbling, or stress and crazing. Bend the acrylic sheet away from the heat source. Accelerate the cycle time by placing heating elements above and below the acrylic sheet. Visible bowing of the acrylic sheet may occur on bends that are longer than 24". To reduce the amount of warpage, minimize the width of the heated area, heat the entire bend evenly, perpendicular to the sheet’s manufacturing direction, and clamp the sheet in place while being heated and cooled.

Oven Heating Sheet

An entire sheet of Plaskolite acrylic can be heated to forming temperature in an oven. Acrylic sheet can be hung in a vertical oven, or clamped around all four edges and placed in a horizontal oven. Manufacturing orientation of the sheet, shrinkage, and heating uniformity are important factors when determining heating and forming methods.

Sheet temperature is critical. If not heated enough, the sheet will not acquire good part definition, too hot and the acrylic will pick up mark-of f from minor imperfections in the mold.

Mold temperature is important for good part definition, and to provide gradual cooling to minimize stress and crazing.

Drape Forming

After reaching forming temperature, the acrylic sheet is draped over a mold covered with flocked rubber or flannel.

Free Blown Forming

By clamping heated acrylic sheet beneath a forming template, and applying compressed air through an orifice, the sheet can be blown up similar to blowing a bubble. This method can be reversed by drawing the sheet into a chamber using vacuum pressure.

Thermoforming

Plaskolite acrylic sheet is heated to its forming temperature, placed over a mold, creating an air- tight seal. Vacuum is drawn through the mold, pulling the sheet to it. Once the part takes the shape of the mold, it is slowly cooled, then released.

Typical for signage, Figure 20 shows a method for low volume production. The acrylic sheet is heated while on the mold, vacuum applied. Angle iron presses out any webbing or wrinkles on the flange, and prevents any vacuum loss during cooling. Since the sheet is not clamped in this method, allow for shrinkage in the machine direction.